In vitro Antimicrobial Activity and the Mechanism of Berberine Against Methicillin-Resistant Staphylococcus aureus Isolated from Bloodstream Infection Patients

Figures & data

Table 1 The MIC Value of Berberine Among Different MLST Types of MRSA

MLST Type	Labels	MIC (μg/mL)
ST239	A, B, D, E, H, L, M, O	128.64
ST5	C, G, I	64,128,>2048*
ST2123	F	128
ST344	J, K	128
ST59	N	128
ST39	Control	256

Notes: *Berberine can not be dissolved completely at this high concentration(>2048mg*L⁻¹).

Table 2 MIC and FIC Index of CLI and RIF in the Presence of BER Against MRSA Strains

Labels	MIC(μg/mL)		FIC	MIC(μg/mL)		FIC
	CLI	CLI +BER		RIF	RIF+BER
A	0.50	0.02	0.28	128.00	8.00	0.31
B	0.50	0.13	0.75	256.00	8.00	0.28
C	0.06	0.03	0.75	0.13	0.00	0.52
D	1024.00	256.00	0.50	256.00	8.00	0.28
E	1024.00	32.00	0.16	256.00	8.00	0.28
F	0.13	0.02	0.38	256.00	8.00	0.28
O	512.00	64.00	0.38	0.13	0.00	0.27
H	0.25	0.02	0.31	256.00	8.00	0.28
J	0.13	0.02	0.38	256.00	8.00	0.28
K	512.00	32.00	0.31	256.00	8.00	0.28
L	512.00	32.00	0.31	256.00	16.00	0.31
M	0.25	0.02	0.31	256.00	8.00	0.28
N	512.00	32.00	0.19	0.06	0.00	0.27
O	0.25	0.02	0.19	256.00	8.00	0.31
Control	1024.00	32.00	0.28	0.06	0.00	0.28

Table 3 The Antibacterial Activity of BER in Combination with CLI and RIF Against MRSA Strains (%, n/N)

Antibiotics	Synergism	Indifferent	Antagonism	Unknown
CLI	80.0 (12/15)	13.3 (2/15)	0 (0/15)	6.7 (1/15)
RIF	86.7 (13/15)	6.7 (1/15)	0 (0/15)	6.7 (1/15)

Figure 1 The time-killing curves for BER alone and in combination with RIF or CLI against MRSA strains; (A–C): Control (D–F): ST239. The data are the mean ±SD of colony counts at least two biological replicates in each group.

Table 4 The Percentage of Biofilm Formation Inhibited

Strains	BER Alone					BER in Combination with CLI					BER in Combination with RIF
	4×MIC BER	2×MIC BER	1×MIC BER	1/2×MIC BER	1/4×MIC BER	BER	CLI	1/4 BER	1/4 CLI	1/4 BER +1/4 CLI	BER	RIF	1/4 BER	1/32 RIF	1/4BER +1/32 RIF(1/16 RIF)
Control	71.80%	39.84%	24.73%	8.81%	1.80%	81.09%	69.33%	46.58%	57.26%	74.75%	75.11%	69.17%	44.64%	62.64%	82.67%
ST239	95.65%	89.92%	75.03%	2.04%	-119.20%	94.48%	69.09%	44.69%	56.07%	71.46%	99.06%	58.17%	38.19%	44.36%	65.24%

Notes: The percentage of inhibited was that biofilm formation compared with positive control in each group and was calculated using the mean.

Figure 2 The effects of BER alone on biofilm formation of MRSA strains. (A) Control (B) ST 239; relative biofilm formation levels were represented as mean±SD of at least two biological replicates; significant difference was determined at P < 0.0001 with comparison between the groups.

Figure 3 The effects of BER in combination with RIF or CLI on biofilm formation of MRSA strains. (A and B): Control (C and D): ST 239; relative biofilm formation levels were represented as mean±SD of at least two biological replicates; significant difference was determined at P < 0.0001 with comparison between the groups.

Figure 4 The effect of BER on cell membrane integrity of MRSA strain by confocal laser scanning microscopy.

Figure 5 The changes in the morphology of MRSA cells with BER by field emission scanning electron microscope. (A and E): 0×MIC; (B and F): 1×MIC; (C and G): 2×MIC; (D and H): 4×MIC. Shown by the arrow is flocculent substances.